Temps

[Pete Masterson]

===============================================

Pete Masterson, Author of

Book Design and Production: A Guide for Authors and Publishers

"Aeonix1@Mac.com"

Aeonix Publishing Group    http://www.aeonix.com

===============================================

On Jun 17, 2008, at 10:46 PM, Glenn Allen wrote:

Pete,

Good Summary.  Can you or someone elaborate on the following 

questions I have about the areas of your post noted below relative 

to a 1986 PT-40 6V92.

Thanks,

Glenn....(see questions noted below your comments):

The transmission cooler is in the bottom of the  

water radiator. The other radiator you see is not the 

transmission cooler. (I don't think it even has a fan.) The air   

flow through the transmission cooler is from the main radiator 

fan. 

1a) There is a small radiator attached on the outside bottom left of 

the main radiator that has hoses running to the power stearing fluid 

cannister.  I assume this small radiator is cooling the fluid for 

power stearing and the hydraulic fan.  There is also a round 

cannister down low that is between the driver's side of the engine 

and the main radiator with large diameter (3"+) hoses from the 

radiator and engine.  There are also lines from the transmission.  

I'm assuming this is the transmission heat exchanger.  I would 

assume water is flowing from the bottom of the radiator to the 

transmission cooler and then to the engine.  Is this correct?  

I'd have to go out to the coach and take a look. I don't recall the "canister" you mention (it might be there, but I don't recall it). The bottom (1/4 or so?) of the water radiator is a radiator for the transmission fluid. When my radiator core was removed, there was a 'stub' radiator for the transmission fluid. The new core attached above it. I no longer recall if water moved through some of the tubes and transmission fluid moved through the other tubes or exactly what the physical arrangement was. 

The second small radiator is for cooling the power steering (and may cool the hydraulic fan fluid as well). The power steering reservoir is a large canister on the curb side visible through both the rear and side doors. Do not overfill it. If you do, it will coat everything nearby with oil. (And I'm not going back to that place for service again.)

The fan pulls air through a 'stack' of radiators. You can remove the grill on the street side and you'll see (I'm going by memory here, so bear with me) the AC condenser, and the Air Charge cooler. Behind the air charge cooler is the regular water radiator with the transmission radiator in the bottom portion of it. You can't see the water/transmission radiator since it's fully covered by the Air Charge cooler. 

Looking from the inside, you mostly see the fan and the metal shroud that makes the fan more efficient.

1b)I notice on this transmission cooler there are plugs on each 

end.  Do these plugs drain the water or transmission fluid from the 

heat exchanger (or maybe both)?  

Afraid I don't know. I have a 400+ page DD Series 60 manual (as a PDF). Perhaps I can make a copy available to you if you'd like. (I bought a CD with it on eBay.) I don't know if this manual discusses the radiator set up in the coach (bus) as it's mostly focused on heavy truck installations. More likely this is covered in Allison documentation -- I don't have any of that stuff beyond the owner's manual.

1c)Should this transmission cooler be cleaned or serviced?

The transmission fluid filters should be changed every 36 or 48 months depending on the size of filters you have. (I have to check this.) These are located in the transmission 'pan'. When the filters are changed the transmission fluid is also changed. Use a synthetic transmission fluid (I have Transynd). I don't think there's any specific service required for the cooler itself. You change the transmission fluid on the same interval as the filters. With an RV you're going to probably "time out" rather than exceed the suggested miles.

Change the engine oil (and filters) every year or 15,000 miles, whichever comes first. A full oil change will take nearly 40 quarts (10 gallons) of oil. You can use a synthetic, if you wish, but the change interval is the same. I have Rotella or Delo for heavy duty diesel engines.

There is a canister on the curb side that holds about 3 gallons of oil and there's an automatic oil add system (requires air pressure to operate), if needed.

I think it comes on at 190 or so ... or whenever you turn on 

the "fan override" switch  

or turn on the dash AC.

2a) I believe my fan is "always on".  When the engine temp is cool, 

the AC is off, and the fan override is off, should the fan be 

turning at idle speed or stationary?

The fan should be not turning or turning very slowly at idle speed if the engine isn't fully warm. They fan will run at full speed if _either_ the "fan override" or AC switch (the little button on the automotive heat control panel) are on.

2b) Is the speed of the fan proportional to the engine RPM?

Not that I'm aware of. I think it has two or three speeds. Frankly, I've never paid much attention to the fan when it was operating. I've verified that it works and I've seen the clouds of dust it kicks up when it's on, though.

3b) Where is the relay that the fan override switch controls?

Front load center, SK 68 is the fuse. Relay K39 says "Chassis A/C Eng. Fan Enable" -- I don't see any other relay related to the Fan. I suppose that the fan override switch tickles the same relay as the AC switch.

There area two other main Load Centers. One is behind the cabinets above the dashboard (on the right). The cabinets have a false back that pulls out, revealing the TV aerial wires and a load center. There's also a load center in the rear closet on the street side behind a felt-covered door.